![]() The characteristic frequency and sensitivity of the auditory receptors increased while latency decreased with increasing temperature. In fact, Oldfield( Oldfield, 1988) discovered that, in the locust, tuning and sensitivity of single auditory receptors are temperature dependent. Because hearing mechanisms depend on electrochemical transduction which is likely to be affected by temperature, we might expect the auditory pathway to be temperature sensitive. Fonseca and Revez ( Fonseca and Revez,2002b) showed that, at least in three species of cicadas, some temporal parameters of their songs are deeply affected by changes in temperature. josei is active during the day in June and July,usually singing at ambient temperatures from 22☌ to 35☌. Tettigetta josei, the experimental model insect species in the present study, exhibits this fine frequency resolution as revealed by the response of its auditory ascending interneurons which are sharply tuned and cover a large range of frequencies, including around the peak of the calling song – 16 kHz ( Fonseca et al.,2000).Ĭicadas are essentially ectothermic insects( Fonseca and Revez, 2002b Sanborn et al., 1992) and therefore fluctuations in environmental temperature might influence auditory processing. Cicadas have up to 2000 receptor cells per ear, with a high frequency resolution that is maintained at the level of the central nervous system (CNS)( Fonseca et al., 2000 Fonseca and Revez, 2002a). Cicadas evolved a sophisticated auditory pathway capable of a fine discrimination of sound parameters, such as the spectral content and the temporal pattern of a signal( Daws et al., 1997 Fonseca and Revez, 2002a Sueur and Aubin, 2002). Precise recognition of the species-specific signal is essential, especially when other sound communicating species are present, because the cicada must discern the song of its own species( Huber, 1984). Acoustic communication is important for several behaviors, such as recognition of conspecifics, localization of the sender, mate choice and predator detection. Like many other species of insects ( von Helversen and von Helversen, 1994 Stumpner and von Helversen,2001) cicadas have developed highly specialized systems of intraspecific acoustic communication in the course of evolution. ![]() Thus,potassium channels are implicated in the tuning of the receptor cells. TEA caused shifts on tuning and sensitivity of the summed response of the receptors similar to the effects of temperature. Since the above mentioned effects of temperature are present in the auditory nerve recordings, the observed shifts in frequency tuning must be performed by mechanisms intrinsic to the receptor cells.įinally, the role of potassium channels in the response of the auditory system was investigated using a specific inhibitor of these channels,tetraethylammonium (TEA). Laser vibrometry measurements revealed that the vibrations of the tympanum and tympanal apodeme are temperature independent in the biologically relevant range(18–35☌). ![]() Secondly, we investigated the role of the mechanical sensory structures that participate in the transduction process. Different tuning mechanisms underlying frequency selectivity may explain the results observed. Characteristic frequency shifts were only observed at low frequency (3–8 kHz). Increasing temperature led to an upward shift of the characteristic hearing frequency, to an increase in sensitivity and to a decrease in the latency of the auditory response both in the auditory nerve recordings (periphery) and in some interneurons at the metathoracic–abdominal ganglionic complex (MAC). The activity of the auditory nerve and the responses of auditory interneurons to stimuli of different frequencies and intensities were recorded at different temperatures ranging from 16☌ to 29☌.įirstly, in order to investigate the temperature dependence of hearing processes, we analyzed its effects on auditory tuning, sensitivity, latency and Q 10dB. The effects of temperature on hearing in the cicada Tettigetta josei were studied.
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